A climate scenario refers to a plausible future climate, and a climate change scenario, implies the difference between some plausible future climate and the present-day climate. The Climate scenarios are in turn driven by greenhouse gas scenarios, which are again built around the plausible future paths that a society may take. Under the aegis of NATCOM, both climate and GHG emission scenarios have been developed to have a peak at the likely future conditions when climate change will prevail. The following section discusses some of the results of the projections made by the climate and GHG emission models.

Construction of Climate scenarios for India

State-of-art coupled Atmosphere-Ocean General Circulation Models (AOGCMs) using three types of future greenhouse gas emission scenarios (IS92a, A2 and B2) and a regional climate model (HadRM2) using only IS92a have been run for projecting the rainfall and temperature scenarios upto the middle of the 21st century. Apart from developing scenarios for temperature and rainfall, high-resolution HadRM2 simulations are also used to study extreme climate events and their future projections over India. Model simulations under scenarios of increased greenhouse gas concentrations indicate marked increase in both rainfall and temperature into the 21st century, particularly becoming conspicuous after the 2040's.

There is considerable inter-model dispersion in the case of monsoon rainfall projections, while the models show a better consensus in their temperature projections. While the scenarios presented in this study are indicative of the expected range of rainfall and temperature changes, it must be noted that the quantitative estimates still have large uncertainties associated with them. Evaluation of HadRM2 performance has been done on the basis of different indices representing extremes such as the mean number of rainy days, intensity of rainfall on a rainy day, annual extreme rainfall, etc. For temperature, the magnitudes of extremes in maximum and minimum temperatures are considered. The model reproduces the spatial patterns of rainfall and temperature extremes quite reasonably while some systematic biases of under/over estimation of extremes are noted across the country.

The analyses carried out show that there is a general tendency for the number of rainy days all over the country to show some decline while the mean intensity of rainfall on a rainyday increases in the increased greenhouse gas (GHG) simulations. The extremes in both rainfall and temperature (maximum and minimum) generally show an increase in the GHG simulations over the country.

Spatial patterns of projected seasonal surface air temperature change (°C) by HadRM2 for 2050s relative to 1990s, under transient increase of greenhouse gas concentrations.	Spatial patterns of projected seasonal precipitation change (mm) by HadRM2 for 2050s relative to 1990s, under transient increase of greenhouse gas concentrations.

GHG emission scenarios

The future greenhouse gas (GHG) emissions depend on the development pathways driven by economic, demographic, land use, agricultural, technological and energy drivers. The interactions among these key-drivers are complex and have profound regional specificity. Significant regional and sectoral variability in resource endowment and economic development exists within India. The future states of India's development are visualized as four scenarios differentiated by the extent of market integration (extent of liberalization and integration with global markets) and type of governance (centralization or decentralization). Four Indian (referred with prefix I) scenarios are named IA1, IA2, IB1 and IB2 to follow IPCC SRES scenarios. The plausibility of scenarios thus exists within the Indian reality.

The IA1 scenario, for instance, can be interpreted as the early and rapid diffusion of the dynamics that already exist in economically advanced states within India. Pathways for carbon dioxide (CO₂) emission that correspond to each scenario are projected using an integrated energy systems modeling framework. Emissions for the other five GHGs are projected with suitable techniques. While the research is agnostic about the probability for realization of a scenario, the IA2 scenario is treated as reference for discussing the key results. Some of the key findings for the period 2000 to 2030 for IA2 scenario suggest that the four fold increase in GDP shall be accompanied by increase in CO₂ emissions by 2.8 times, methane by 1.3 times, nitrous oxide by 2.6 times and other three fluorochemical GHGs (combined) by 15 times.

The extraordinarily high growth of fluorochemical GHGs is due to small initial base and rapidly increasing emissions of HFC-23. While the emissions in Indian reference scenario IA2 rises at rates higher than those globally observed in SRES A2 scenario the per capita GHG emissions for the basket of six gases for India would still be only 2.56 tons-CO₂ equivalent/capita in 2030 - which would remain significantly below the global average. The emissions scenarios developed follow the IPCC emission scenarios. Policy relevant scenario developments call for wider consultation and validation via a national process.

Future GHG emission projections under business-as-usual (IA2) scenario in CO₂ equivalent terms (Million tons per year)

---

GEF Project Implemented by UNDP

Implementing & Executing Agency Ministry of Environment and Forests Government of India

Facilitating Agency Winrock International India

© 2004 Natcom India
The views and opinions expressed in these newsletters are those of the authors. NATCOM India does not endorse or refute any of the views and/or opinions expressed in these articles